Calcium Complexes Research Articles

Structural characterization of calcium-binding sunflower seed and peanut peptides and enhanced calcium transport by calcium complexes in Caco-2 cells.

Peptide-Ca complexes can promote Ca absorption. The present study aimed to determine the transport mechanism and structural characteristics of sunflower seed and peanut peptides with high Ca binding capacity with respect to developing third-generation Ca supplements and functional food ingredients. High Ca-binding fractions of 1-3 kDa sunflower seed peptide (SSP4 ) and ≥ 10 kDa peanut peptide (PP1 ) had higher amount of Ca transported than CaCl2 and two hydrolyzed proteins in Caco-2 cells. SSP4 and PP1 were separated by Ca ion metal chelate affinity chromatography, and high Ca-binding fractions were observed for SSP4 -P2 and PP1 -P2 . The amino acid sequences of SSP4 -P2 and PP1 -P2 were characterized by high-performance liquid chromatography-electrospray ionization-time of flight mass spectrometry. Seven and eight peptides were identified from SSP4 -P2 and PP1 -P2 , respectively. These peptides had molecular weights ranging from 1500 Da to 2500 Da and a large number of characteristic amino acid sequences, such as EEEQQQ, EQ-QQQ-QQ, QQ-QQQQQ, E-EEE, EE-EEQ, RR, Q-QQ-QQQ, EE-EQ-EE-Q, QQ-QQQQ, and Q-QQQQ, where 'E' is glutamic acid and 'Q' is glutamine. SSP4 and PP1 can promote Ca transport in Caco-2 cells without affecting cell permeability. The amino acid sequences of SSP4 -P2 and PP1 -P2 with high Ca-binding abilities contain characteristic sequences, such as continuous glutamic acid and glutamine, and have low molecular weights. © 2020 Society of Chemical Industry.

Magnesium and calcium complexes bearing mono-oxidized or monoprotonated acenaphthylenebisamido ligand: Structure features and ROP activity

Acenaphthylenebisamido metal complexes (dpp-bian)Mg(thf)3 and (dpp-bian)Ca(thf)4 by reaction with azobenzene and dicumyl peroxide, respectively, give paramagnetic species [(dpp-bian)Mg(thf)NPh]2 (3) and (dpp-bian)CaOCMe2Ph(dme) (4) containing monoanionic dpp-bian ligand. Treating the parent compounds with 1 equiv of 2,6-di-tert-butyl-4-methylphenol leads to formation of amino/amidoacenaphthylene-supported complexes (dpp-bianH)MgO(tBu2MeC6H2)(thf) (5) and (dpp-bianH)CaO(tBu2MeC6H2)(thf)2 (6) featuring ancillary bulky phenoxido ligand. As NMR studies confirm, a sterically demanding moiety in the magnesium coordination sphere hinders the intramolecular shuttle proton transfer in 5, whereas calcium complex 6 maintains typical dynamics in solution. Compounds obtained show a modest activity in ROP of L-lactide in toluene. In particular, 3 and 4 prove to be active for moderate-controlled polymerization, whereas 5 and 6 give broadly dispersed PLAs.

Исследование влияния антибиотиков на скорость реминерализации зубной эмали

The safety of antibiotics is still debatable. The properties of large molecules to give insoluble compounds with metal ions leads to a decrease of absorption of active components and most often loss of biological activity. Depending on the presence of functional groups in the side chain, the formation of complexes of different strength is possible. The properties of a number of antibiotics to interact with calcium ions allow us to expect the interaction of these antibiotics with the surface of the tooth enamel along the calcium centers. The alkaline environment of the oral cavity and the excess of calcium ions in the saliva, in comparison with phosphate residues, make it possible to make available the calcium centers of the hydroxyapatite crystal. The strength of this complex will be determined by the structure and functional substituents of the antibiotic molecule and will not depend much on its charge. In this article the effect of broad-spectrum antibiotics on the remineralizing ability of saliva in relation to tooth enamel based on the experiments performed on teeth is discussed. The analysis of the degree of remineralization function of saliva was carried out by means of spectrophotometric determination of the stability of calcium complexes with individual broad-spectrum antibiotics at different multiplicity of individual components. As a result of setting up an experiment to restore tooth enamel after treatment with these solutions of antibiotics, the characteristic assessment of which is the presence of sites of remineralization and their size on the surface of the tooth enamel for certain periods of time and in comparison with the standard, it was concluded that antibiotic solutions reduce the remineralization ability of saliva to restore the outer surface of the enamel of teeth.

ОПТИМИЗАЦИЯ УСЛОВИЙ СИНТЕЗА КОМПЛЕКСНОЙ СОЛИ КАЛЬЦИЯ

The conditions for the synthesis of calcium complex salt in 10, 20, 30, 40, 45% mother liquors at temperatures of 20, 40, and 60°C were studied. The optimal values of the synthesis technological process were obtained, such as the concentration of the starting reagents, time and pH. The solubility of EDTA with respect to calcium carbonate was determined.

Slow lactate gluconate exchange in calcium complexes during precipitation from supersaturated aqueous solutions

Saturated solutions of calcium l-lactate in water or in deuterium oxide continuously dissolve calcium l-lactate by addition of solid sodium d-gluconate and become strongly supersaturated in calcium d-gluconate due to no or slow precipitation. The quantification of total dissolved calcium allied with the calcium complexes equilibrium constants allowed an ion speciation, which shows an initial non-thermal and spontaneous supersaturation of more than a factor of 50 at 25 °C only slowly decreasing after initiation of precipitation of calcium d-gluconate after a lag phase of several hours. A mathematical model is proposed, based on numerical solution of coupled differential equations of dynamics of l-lactate and d-gluconate exchange during the lag phase for precipitation and during precipitation. A slow exchange of l-lactate coordinated to calcium with d-gluconate is indicated with a time constant of 0.20 h−1 in water and of 0.15 h−1 in deuterium oxide and a kinetic deuterium/hydrogen isotope effect of 1.25. Such spontaneous non-thermal supersaturation and slow ligand exchange with a pseudo first order equilibration process with a half-life of 3.5 h in water for calcium hydroxycarboxylates can help to understand the higher calcium bioavailability from calcium hydroxycarboxylates compared to simple salts.

Effects of combined measures to minimize white efflorescence formation on dry fermented sausages co-extruded with alginate casings.

On dry fermented sausages, especially co-extruded with calcium alginate casings, the formation of white crystals on the surface of the product is a common problem. In this study a hurdle system of combinations of different metal complexing chelators (citric acid and polyphosphate) was investigated. The control and the sample produced with 1.1% citric acid in the alginate gel showed strong white efflorescence formation during the storage (∼60% of the surface was covered), whereas the samples with added 0.3% polyphosphate showed no efflorescence formation. The efflorescence-causing substances such as lactate, magnesium, and calcium increased significantly in the samples, which showed the strongest white efflorescence formation. In the control, lactate increased by 45.0%, calcium by 23.9%, and magnesium by 150.8%, whereas in the samples without white efflorescence, the magnesium and lactate content increased only slightly, and the calcium content even decreased during the storage of 8 weeks. The best results were observed on the addition of 0.3% polyphosphates and the citric acid surface treatment directly after the co-extrusion. Moreover, the strong complex formation could be due to the complexation of magnesium and calcium by lactate, whereby they are removed from the diffusion equilibrium leading to an increased diffusion of the efflorescence-causing substances. PRACTICAL APPLICATION: White efflorescence formation on dry fermented sausages is a major problem on dry fermented sausages, which causes food waste and financial loss for the producer. This study investigated different combinations of promising methods and it was possible to inhibit the white efflorescence formation during the storage. The methods are easy to implement during the manufacturing of the products and are therefore quite interesting for the industrial applications.

Phosphorus binding to soil organic matter via ternary complexes with calcium

Soil organic matter (SOM) is known to exert a major control on the mobility and bioavailability of cationic nutrients. However, the role of SOM in the fate of anionic nutrients, especially phosphorus (P), is less well characterized. The objectives of this study were to (1) compare the formation of binary complexes of calcium (Ca) with humic acids (HA) extracted from two contrasting soils, and (2) determine if binary HA-Ca complexes could incorporate P by forming ternary HA-Ca-P complexes. The Ca binding capacities of the HA extracted from an agricultural organic soil (AOS) and a pristine riparian soil (RS) were measured via potentiometric titrations; the formation of ternary complexes was analyzed by size fractionation using MWCO tubes. Proton and Ca binding capacities of RS-HA were higher than AOS-HA, and pH had a weaker effect on Ca binding to RS-HA. These differences are consistent with lower proportions of aromatic groups, and a higher proportion of alkyl groups derived from 13C NMR spectroscopy. Together, the NMR, titration and MWCO data indicate that Ca binds to RS-HA through monodentate complexes and electrostatic attraction that are capable of binding P producing ternary complexes. In contrast, at pH 8.5 Ca forms bidentate complexes with AOS-HA, which do not provide bridging positions to incorporate P. Overall, our results imply that the formation of HA-Ca and HA-Ca-P complexes depend on the structure of the HA, and that complexation to HA may play an important role in the fate of P in terrestrial and aquatic environments.

The Depressing Effect of Kaolinite on Molybdenite Flotation in Seawater

Copper-molybdenum grades of important mining deposits have progressively decayed, which is associated with high levels of clay minerals which affect froth flotation. The depressing effect of clay minerals on copper sulfides was previously reported but there are no systematic studies on the effect on molybdenite flotation in seawater. The objective of this work was to study the effect of kaolinite on molybdenite flotation in seawater and to evaluate the use of sodium hexametaphosphate (SHMP) as dispersant. The results of this work show that kaolinite depresses molybdenite flotation which is more significant in seawater at pH > 9. All the experimental data validate the hypothesis that kaolinite covers molybdenite, reducing its flotation recovery. The depressing effect of kaolinite on molybdenite flotation in seawater is enhanced by the magnesium and calcium hydroxo complexes at pH > 9, which induce heterocoagulation between kaolinite and molybdenite, thus reducing recovery. The attachment of the positively charged hydroxo complexes of magnesium and calcium to the molybdenite and kaolinite surfaces is diminished by SHMP. This reagent increases the repulsive forces between molybdenite and precipitates and as a result, molybdenite becomes more hydrophobic and recovery increases.

Reactivity of a Molecular Calcium Hydride Cation ([CaH]+) Supported by an NNNN Macrocycle.

The hydride ligand in the cationic calcium hydride supported by a NNNN-type macrocycle, [(Me4TACD)2Ca2(μ-H)2(THF)][BAr4]2 (1; Me4TACD = 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane; THF = tetrahydrofuran; BAr4 = B(C6H3-3,5-Me2)4), shows, in addition to its Brönsted basicity toward weak acids, a pronounced nucleophilicity resulting in nucleophilic substitution or insertion (addition) at a silicon or sp2 carbon center. Terminal acetylenes RC≡CH (R = SiMe3, cyclopropyl) as well as 1,4-diphenylbutadiene were deprotonated by 1 to give dinuclear complexes [(Me4TACD)2Ca2(μ-C≡CR)2][BAr4]2 (2a, R = SiMe3; 2b, R = cyclopropyl) and [(Me4TACD)2Ca2(μ2-η4-1,4-Ph2C4H2)][BAr4]2 (3) with H2 evolution. The addition reaction with BH3(THF) gave a tetrahydridoborate complex, [(Me4TACD)Ca(BH4)(THF)2][BAr4] (4), with κ2-H2BH2 coordination in the solid state, suggesting a pronounced Lewis acidic calcium center. The behavior resulting from both Lewis acidity and hydricity becomes apparent in the nucleophilic substitution of fluorobenzene by 1 to give benzene and the dimeric fluoride complex [(Me4TACD)2Ca2(μ-F)2(THF)][BAr4]2·2.5THF (5). Analogous nucleophilic substitution reaction is observed for heterofunctionalized organosilanes XSiR3 [X = I, N(SiHMe2)2, N3; R = Me3 or HMe2], which resulted in the formation of calcium complexes [(Me4TACD)Ca(X)(THF)n][BAr4] (6-8) containing an X ligand along with hydrosilane HSiR3. An insertion reaction by 1 was observed with CO2 and CO to give dinuclear formato complex [(Me4TACD)2Ca2(μ-OCHO)2][BAr4]2 (9) and cis-enediolato complex [(Me4TACD)2Ca2(μ-OCH═CHO)][BAr4]2·3.5THF (10), respectively. The latter is believed to have been formed as a result of the dimerization of an initially generated formyl or oxymethylene complex, [(Me4TACD)Ca(OCH)]+.

Synthesis, spectroscopic, thermal, structural investigations and biological activity studies of charge-transfer complexes of atorvastatin calcium with dihydroxy-p-benzoquinone, quinalizarin and picric acid

The charge-transfer interactions between n-electron donor, atorvastatin calcium (ATC) and the electron acceptors, 2,5-dihydroxy-1,4-benzoquinone (DHBQ), 1,2,5,8-tetrahydroxy-9,10-anthraquinone (quinalizarin, Quiz), and 2,4,6-trinitrophenol (picric acid, PA) as π-acceptors have been studied spectrophotometrically in methanol by giving highly colored charge transfer complexes. The isolated solid charge-transfer complexes were characterized by elemental, IR, NMR, mass and thermal analysis to elucidate the chemical structure of the obtained solid CT complexes. The stoichiometry of the complexes was found to be 1:2 in [ATC]:[reagent] at DHBQ, quinalizarin, picric acid. This ratio gave the formed charge-transfer complexes in the formulas [(ATC)(DHBQ)2], [(ATC)(Quiz)2], and [(ATC)(PA)2] which was also confirmed by elemental and mass analysis. Their biological activities were also screened against various bacterial organisms. The obtained results are suitable for the estimation of antihyperlipidemic drug, ATC in pharmaceutical dosage forms.

Polydatin improves osteogenic differentiation of human bone mesenchymal stem cells by stimulating TAZ expression via BMP2-Wnt/\u03b2-catenin signaling pathway

ObjectivesPolydatin (PD), extracted from Polygonum cuspidatum, has shown potential therapeutic applications due to its antiosteoporotic and anti-inflammatory activities. Our previous study suggested that PD promotes the osteogenesis of human bone marrow stromal cells (hBMSCs) via the BMP2-Wnt/β-catenin pathway. The aim of our present study was to further explore the role of PD-mediated regulation of Tafazzin (TAZ), a transcriptional coactivator with a PDZ-binding motif, in osteogenesis.Materials and methodshBMSCs were isolated and treated with PD at various concentrations. Alizarin red staining and RT-qPCR were performed to identify calcium complex deposition in hBMSCs as well as the expression of specific osteoblast-related markers, respectively, in each group. Next, TAZ-silenced hBMSCs were generated by lentivirus-produced TAZ shRNA. After treatment with PD, the osteogenic abilities of the TAZ-silenced and control hBMSCs were estimated by ALP activity assay, and expression of the TAZ protein was detected by Western blot analysis and immunofluorescence staining. In vitro, an ovariectomized (OVX) mouse model was established and used to evaluate the effect of PD on bone destruction by micro-CT, immunohistochemistry, and ELISA.ResultsIn vitro, 30 μM PD significantly improved the proliferation and calcium deposition of hBMSCs and markedly stimulated the expression of the mRNAs RUNX2, Osteopontin, DLX5, β-catenin, TAZ, and Osteocalcin (OCN). Osteogenic differentiation induced by PD was blocked by lentivirus-mediated TAZ shRNA. Furthermore, Noggin (a regulator of bone morphogenic protein 2 (BMP2)) and DKK1 (an inhibitor of the Wnt/β-catenin pathway) were found to inhibit the increase in TAZ expression induced by PD. In vivo, PD prevented estrogen deficiency-induced bone loss in the OVX mouse model.ConclusionTaken together, our findings suggest that PD improved the osteogenic differentiation of hBMSCs and maintained the bone matrix in the OVX mouse model through the activation of TAZ, a potential target gene of the BMP2-Wnt/β-catenin pathway.

Functional wheat bread with calcium chelate complexes

Bakery products are promising objects for enrichment with functional food ingredients, as they are mass consumption products. The problem of hypo-elementosis in people makes it advisable to develop functional food ingredients based on easily digestible and safe forms of essential biometals, including calcium. In this study, it has been shown that wheat bread can be enriched with calcium chelate complexes. This functional food ingredient was obtained by complexation of Ca2+ with bioligands of probiotic origin, followed by immobilizing the complexes on dietary fiber of wheat bran. Mixed-ligand systems were obtained by combining a metabolite (lactic acid) and degradation products of peptidoglycans of Lactobacillus delbrueckii subsp. Bulgaricus B-3964. The peptidoglycans of the biomass autolysate were degraded by enzymatic hydrolysis with papain. This resulted in obtaining a mixture that contained amino acids, low molecular weight peptides, and muropeptides, in the concentrations 12.44 mg/cm3, 6.85 mg/cm3, and 2.76 mg/cm3, respectively. The nephelometric method has shown that this mixed-ligand system binds calcium ions in an amount of 18 mg/cm3. The soluble complexes obtained were immobilized on the dietary fiber to solve the problem of concentrating, drying, and dosing these ingredients. It has been proved that immobilization only occurs due to physical sorption that completely releases the active component from the dietary fiber matrix under conditions that simulate the gastrointestinal environment. The functional ingredient developed was added to the classic wheat bread recipe, where it replaced 1 %, 3 %, and 5 % of the flour. Bread was made without pre-fermentation to reduce the total production time and to prevent the ingredient’s biologically active components from being assimilated by yeast during long fermentation. The study of the experimental and control samples of wheat bread has shown that the introduction of chelate complexes of calcium immobilized on dietary fiber causes no deterioration of the physico-chemical parameters of the finished bread: they are all within the limits approved by the regulatory documentation. The sensory properties of the samples with 1 % and 3 % of flour replaced are close to those of the control sample. So 3 % of the ingredient is the recommended amount to be added, as it provides 98 % of the daily requirement of calcium as a functional ingredient and covers about 25 % of the daily allowance of dietary fiber.

Calcium-iron-D-gluconate complexes for the indirect cathodic reduction of indigo in denim dyeing: A greener alternative to non-regenerable chemicals

With an annual production of approximately 7–10 billion m2 the manufacturing of indigo dyed denim takes a substantial share in global textile production. At present the vast majority of dyeing processes with indigo still bases on the use sodium dithionite as reducing agent. For a successful replacement of the non-regenerable reducing agent by electrochemical processes, a combination of a regenerable redox system with an appropriate cell design is required. In the presented study, the use of embroidered electrodes in an 85 mA flow-through electrolyser for electrochemical indigo reduction has been investigated for the first time. Indirect cathodic reduction of indigo was achieved with use of a 0.1 M solution of a binuclear complex of calcium and iron with D-gluconate as a ligand. The electrochemically reduced indigo was then used in lab scale dyeing (1–3.5 g L−1 indigo), and the results were compared to reference dyeing experiments with sodium dithionite as reducing agent, by measuring the colour strength and CIElab colour coordinates. Comparison of the electrochemical technique for indigo reduction with the dithionite-based standard process indicates substantial potential for an improvement of the ecological profile of the dyeing process used at present. The electrical power demand for a full scale electrolyser is estimated to be in the range of 2.8–6.9 kW, leading to an energy consumption of 58–145 kWh d−1 as compared to a sodium dithionite consumption of 50–126 kg d−1. Introduction of biobased and regenerable chemical systems instead of non regenerable chemicals in indigo dyeing offers significant potential for reduction of the chemical load released into wastewater. A reduction of the sulphate concentration in the wastewater from the current values of 640–1600 mg L−1 to values well below the legal limit of 200 mg L−1 sulphate will be possible. By reuse of the washing water and the reversible reducing agent, a reduction of both water consumption (by 80%) and chemical consumption (by 50%) are expected.

Devising the technological principles for making a granulated filler obtained through ionotropic gelation

This paper reports the development of technological principles for making granulated fillers. Our study involved model systems (granules), which has made it possible to determine the conditions for forming alginate-calcium complexes. It has been established that the basic principle for obtaining the granules is the ratio of mannuronic to guluronic residues in the composition of sodium alginate, which should equal χ=0.4...0.6 to implement the process of granulation. It has been proven that the content of G-blocks in the composition of sodium alginate should be within 20...25 %, which, at the content of ionic calcium within the range of 80 to 120 mg %, ensures the formation of stable alginate calcium complexes. It has been determined that the increase in the module of elasticity of the structured systems depends on the concentration of sodium alginate, the conditions for implementing its sorption properties relative to calcium ions, and the quantitative content of charged particles.The reduction of the sorption capacity of sodium alginate has been proven under a condition of the lowered pH, as there occurs the exchange of ions of sodium for the ions of hydrogen, that is the formation of alginic acids (HAlg), which have a low ability to dissociation and ion exchange. It has been experimentally confirmed that the use of low pH raw materials in the technology of granulated fillers based on sodium alginate would not only reduce the module of elasticity of the granules but could also contribute to the loss of the system transparency.The influence of sugar syrups, pH of the medium, as well as heat treatment, on the module of elasticity and a change in the weight of granulated fillers have been investigated. It has been determined that under the impact of the above factors there is an increase in the module of elasticity of granulated fillers and a decrease in their mass due to a partial release of moisture. Taking the specified technological principles into consideration, a model of the technological system for making granulated fillers has been devised. Specific features of the technological process have been defined under a condition for the use of dairy raw materials, alcohol-containing raw materials, as well as low pH raw materials

Effects of peptide–calcium complexes from sunflower seeds and peanuts on enhancing bone mineral density

SummaryHydrolysed proteins from sunflower seed and peanut were separated by ultrafiltration. Results showed that 1–3 kDa sunflower seed peptide (SSP4) and ≥10 kDa peanut peptide (PP1) fractions had the highest Ca‐binding capacity of 104.80 and 124.74 mg g−1, respectively. After Ca binding, scanning electron microscopy results showed that the loose sheet‐like structure of SSP4 and PP1 transformed into a granular structure. Fourier‐transform infrared spectroscopy results showed that carboxyl and amide groups were involved in Ca binding. Growing male mice were assigned to eight groups: control, CaCO3 and six experimental groups (low, medium and high doses for each SSP4‐Ca and PP1‐Ca). Apparent Ca absorption rate, bone mineral density (BMD), bone surface microstructure and biomechanical index and serum biochemical index were evaluated. Animal experiment results indicated that SSP4‐Ca and PP1‐Ca can improve Ca bioavailability; effectively enhance BMD and structure; and promote Ca absorption. The peptide–Ca complexes were absorbed better than CaCO3 and promoted Ca accumulation in the bone. PP1‐Ca was better than SSP4‐Ca in promoting calcium absorption and enhancing BMD.

Efficacy of Ca2+- or PO4 3--conjugated mesoporous silica nanoparticles on dentinal tubule occlusion: an in-vitro assessment.

BackgroundMaintaining a long-term biological effect of dental materials on dentinal tubule occlusion is one of the great technical challenges in dental clinics. In addition to physical treatment, chemical treatment to produce insoluble precipitates to seal dentinal tubules has been used. As dentin is mostly composed of calcium and phosphate complexes, in this study, we have developed a novel tubule-occluding material [Ca2+/PO43−@mesoporous silica nanoparticles (MSNs)] by separately conjugating either Ca2+ or PO43− with MSNs.MethodsThe shape and structure of the MSNs were examined using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The surface morphology and chemical compositions of Ca2+@MSNs/PO43−@MSNs and Ca2+/PO43−@MSNs were examined using SEM and X-ray fluorescence (XRF). The element distribution of Ca2+/PO43−@MSNs was detected using energy dispersive spectrometer (EDS). The sustained release ability of Ca2+@MSNs/PO43−@MSNs was detected using inductively coupled plasma atomic emission spectrometry (ICP-AES). The efficacy of Ca2+/PO43−@MSNs on dentinal tubule sealing was evaluated using SEM, and the results were analyzed by Image-Pro software to determine the best water-powder ratio. We also compared the sealing efficacy between Ca2+/PO43−@MSNs and NovaMin, which is currently used in clinics, under the simulated conditions of oral acidic corrosion and mechanical friction.ResultsCa2+/PO43−@MSNs are a new type of tubule-occluding material with sustained release properties. The ratio of Ca2+@MSNs: PO43−@MSNs: H2O =0.015 g: 0.015 g: 150 µL exhibited an excellent sealing effect on dentinal tubules as well as resistance to oral acid corrosion and daily oral friction.ConclusionsThe novel dental material Ca2+/PO43−@MSNs demonstrates potential long-term effectiveness in sealing dentinal tubules and reducing dentin sensitivity, which is one of the most important problems in dental clinics.

Thermal Conductivity of Calcium Aluminate and Complex Vanadates of Garnet Structure

The thermal conductivity of materials with the nonstoichiometric garnet structure, namely, of calcium aluminate Са12Al14O33±δ (both single crystal and ceramic) and doped vanadates Ca5Mg4–xMx(VO4)6 (M = Zn, Co; 0 ≤ x ≤ 4), in the temperature interval 50–300 K was studied by the steady state comparative-longitudinal thermal flux method. The compositions Ca5Mg4–xZnx(VO4)6, x =1, 3, 4, were studied in the temperature interval 298–573 K by the dynamic method. The effect of the defective structure on the thermal conductivity of the materials was discussed. The thermal conductivity of the materials is ~2 W m–1 K–1 at room temperature and above.

Controllable preparation of monodisperse alginate microcapsules with oil cores

Here we report a novel strategy for controllable preparation monodisperse alginate microcapsules with oil cores, where the thickness of the alginate shells, as well as the number and diversity of the oil cores can be tailored precisely. Monodisperse oil-in-water-in-oil (O/W/O) emulsions are generated in a microfluidic device as templates, which contain alginate molecules and a water-soluble calcium complex in the middle aqueous phase. Alginate microcapsules are produced by gelling O/W/O emulsions in oil solution with acetic acid, where the pH decreasing will trigger the calcium ions being released from calcium complex and cross-linking with alginate molecules. Increasing the alginate molecule concentration in emulsion templates affects little on the thickness of the microcapsules but improves their stability in DI water. The strength of alginate microcapsules can be reinforced by post cross-linking in calcium chloride, polyetherimide, or chitosan solution. Typical payloads, such as thyme essential oil, lavender essential oil and W/O emulsions are encapsulated in alginate microcapsules successfully. Furthermore, tailoring the thickness of the alginate shells, as well as the number and the diversity of the oil cores precisely by manipulation the emulsion templates with microfluidics is also demonstrated. The proposed method shows excellent controllability in designing alginate microcapsules with oil cores.

A Tale of Biphenyl and Terphenyl Substituents for Structurally Diverse Ketiminato Magnesium, Calcium and Germanium Complexes.

In this paper, we have used two N,O-ketiminato ligands (L1 and L2) with biphenyl and terphenyl substituent on the nitrogen atom. Deprotonation of L1 with KN(SiMe3 )2 and subsequent reaction with MgI2 led to a homoleptic dinuclear magnesium complex (1) with a Mg2 O2 four-membered ring. Deprotonation with nBuLi and subsequent reaction with MgI2 afforded a unusual dinuclear magnesium complex (2) with a Mg2 O2 ring. Extension of the ligand for calcium resulted in a trinuclear calcium complex (3) with six four-membered Ca2 O2 rings. We could not isolate any chelating complex when L2 was used as a ligand, and only oxygen bound magnesium (4) and calcium (5) adducts were isolated. DFT studies were performed to understand this dissimilar behavior. More diverse results were obtained when lithiated L1 and L2 were treated with germanium dichloride. We were able to stabilize a monomeric germylene monochloride (7) with L1. However, with L2, an unusual ligand scrambling, and a C-C coupling take place, leading to the formation of a secondary carbocation with GeCl3 - as a counter-anion (8). Besides, a germanium dichloride adduct (9) bound to the oxygen center of the ligand was obtained as the minor product.

Characterization of novel calcium hydroxide-mediated highly porous chitosan-calcium scaffolds for potential application in dentin tissue engineering.

The aim of this study was to develop a highly porous calcium-containing chitosan scaffold suitable for dentin regeneration. A calcium hydroxide (Ca[OH]2 ) suspension was used to modulate the degree of porosity and chemical composition of chitosan scaffolds. The chitosan solution concentration and freezing protocol were adjusted to optimize the porous architecture using the phase-separation technique. Scanning electron microscopy/energy-dispersive spectroscopy demonstrated the fabrication of a highly porous calcium-linked chitosan scaffold (CH-Ca), with a well-organized and interconnected porous network. Scaffolds were cross-linked on glutaraldehyde (GA) vapor. Following a 28-day incubation in water, cross-linked CH scaffold had no changes on humid mass, and CH-Ca featured a controlled degradability profile since the significant humid mass loss was observed only after 21 (26.0%) and 28 days (42.2%). Fourier-transform infrared spectroscopy indicated the establishment of Schiff base on cross-linked scaffolds, along with calcium complexation for CH-Ca. Cross-linked CH-Ca scaffold featured a sustained Ca2+ release up to 21 days in a humid environment. This porous and stable architecture allowed for human dental pulp cells (HDPCs) to spread throughout the scaffold, with cells exhibiting a widely stretched cytoplasm; whereas, the cells seeded onto CH scaffold were organized in clusters. HDPCs seeded onto CH-Ca featured significantly higher ALP activity, and gene expressions for ALP, Col1, DMP-1, and DSPP in comparison to CH, leading to a significant 3.5 times increase in calcium-rich matrix deposition. In sum, our findings suggest that CH-Ca scaffolds are attractive candidates for creating a highly porous and bioactive substrate for dentin tissue engineering.